Neutron refraction and transmission studied by SESANS

With the newly developed spin-echo technique SESANS very small-angle scattering can be measured of the order 10-5 rad, which in SESANS corresponds to spin-echo lengths Z beyond 3 μm. This small angular changes are measured without confining the divergence of the beam, thus with relatively high intensity. Therefore, the SESANS technique can also be used to measure refraction in wedge shaped materials. The refraction angle is linear in the net precession angle and from that the coherent scattering amplitude density Nb can be derived, Nb=φ tan θ/λZ, where φ is the measured net precession angle, θ the inclination angle of the refracting surface and Z the spin-echo length. From the measurements a loss of amplitude of polarisation is observed, that could be ascribed to intrinsic small-angle scattering in the sample. In this paper first results of SESANS refraction and transmission experiments in aluminium will be presented and discussed